The invention relates to a pressure regulating valve having secondary venting measures, comprising a primary duct subject to a primary pressure, a secondary duct rendering possible tapping of a regulated secondary pressure and a movable control member serving for control of the fluid connection between the primary and the secondary duct, the position of said control member being able to be influenced by a moving setting member able to be subjected to an adjustable presetting force, said setting member being constituted by a movable wall section of a comparison chamber communicating with the secondary duct and said setting member furthermore having a venting opening, also under the control of the control member and serving for venting the secondary duct.
A pressure regulating valve of this type is disclosed in xe2x80x9cDer Pneumatic-Katalog 98xe2x80x9d pages 9.3/12-1. It is utilized more particularly in connection with compressed air handling in compressed air supply networks, it being employed to hold constant the working pressure, available on the secondary side, in a manner substantially independent of variations in pressure on the secondary side. The secondary venting measures here make possible a reduction of the secondary pressure available in the secondary duct, for instance for venting the connected piping or in the case of pressure increases on the secondary side owing to operation of the driven loads.
In the case of known pressure regulating valves there are substantial oscillation problems owing to variations in the secondary pressure. With an increase in the rate of flow or, respectively, a higher utilized flow of the regulator the tendency to oscillation will increase. For reducing the oscillations it is consequently necessary to make the technical performance data of the pressure regulators, and more particularly the maximum achievable flow rates, less than would be otherwise technically possible.
Accordingly one object of the present invention is to provide a pressure regulating valve with a reduced tendency to oscillation.
In order to achieve these and/or other objects appearing from the present specification, claims and drawings, in accordance with claim 1 herein there is the feature that the venting opening is so arranged on the setting member that it is located outside the comparison chamber either directly in the secondary duct or in a region in communication with the secondary duct.
In the prior art the venting opening provided on the setting member is in the interior of the comparison chamber communicating with the secondary duct via a connecting duct. The vented flow occurring with the venting opening open is therefore from the secondary duct through the communicating duct into the comparison chamber and from same by way of the venting opening to the outside. Owing to the limited cross section of the communicating duct, which can be termed an interrogating duct, the pressure obtaining in the comparison chamber falls more rapidly and to a greater extent during venting than the secondary pressure in the secondary duct. This leads to a overshoot of the regulator or, respectively, of the regulating circuit and oscillation of the regulator will occur. Although such tendency to oscillate may be countered by reduction of the size of the venting opening and also by reduction of the cross section of the connecting duct (i. e. physical damping), this will be at the expense of the response behavior of the pressure regulating valve, the excess pressure coming from the fluid distribution network, connected on the secondary side, being able to be reduced less rapidly. In the case of the design of the invention the venting opening responsible for secondary venting is now no longer in the comparison chamber and is located either directly in the secondary duct or in a region which is connected with the secondary duct, for instance in an additional chamber in communication with the secondary duct by way of a large cross section. The pressure available on the secondary side is now still in the comparison chamber and supplies the force opposing the presetting force, which can be set from the outside and with which the secondary pressure to be regulated may be preset. However the vented secondary flow does not pass through the comparison chamber and the connecting duct preceding it, but bypasses the comparison chamber and escapes by way of the venting opening placed outside it. The interfering influence of secondary venting therefore no longer acts on the setting member, something involving the further advantage that the cross section of any connecting duct present may be reduced so that a physical damping of the regulating circuit will take place. An additional advantage will be that the caliber of the venting opening may be increased so that the secondary venting performance is increased. The tendency of the regulator to oscillate is reduced to such an extent that in operation it will oscillate less or not at all and the regulator may be designed and operated for and, respectively, with substantially larger flow performances.
Further advantageous developments of the invention will appear from the claims.
The control member preferably extends in a control chamber designed as component of the secondary duct, the venting opening being within this control chamber. If the control member is in the form of a plunger, the control chamber can also be termed a plunger chamber.
A particularly advantageous design in accordance with the invention is such that the setting member extends in a sealed manner through a housing wall separating the comparison chamber from the secondary duct and has a head section with the venting opening, said head section extending into the secondary duct. Here it is possible for the head section of the setting member to cooperate with a terminal secondary control section of the control member.
Since the control member, unlike the prior art designs, no longer extends through a partition separating the primary duct from the comparison chamber, and instead conveniently terminates within the secondary duct, its terminal section is preferably provided with a guide member placed in the secondary duct and fixed in relation to the housing. This guide means may comprise a guide insert anchored in the above mentioned partition and extending into the secondary duct.
The comparison chamber is preferably connected by way of at least one connecting duct with the secondary duct. This connecting duct can be termed an interrogation duct, because it samples the pressure obtaining in the secondary duct and passes on the information to the comparison chamber.
The connecting duct preferably has a relatively small cross section something which is preferably ensured by providing a suitable choke means. The maximum venting cross section associated with the venting opening may be made larger than the cross section of the connecting duct.
The setting member functioning as a moving wall section of the comparison chamber may be piston-and/or diaphragm-like. It is preferred for it to possess a principal body containing the venting opening and fixed to the housing in a sealing manner by means of a preferably at least partially rubber-elastically deformable diaphragm. This renders possible a setting movement with very little friction.
Further advantageous developments and convenient forms of the pressure regulating valve will be understood from the following detailed descriptive disclosure of one embodiment thereof in conjunction with the accompanying drawing showing a longitudinal section in a single figure.
The drawing shows in longitudinal section a pressure regulating valve generally referenced 1, which could also be termed a pressure regulator. In the present case it is in the form of a so-called servicing device, which is employed for the production or conditioning of compressed air in supply systems and possesses interfaces 2 and 3 preferably arranged on opposite side thereof and serving for the connection of pressure medium lines leading to further equipment or further types of servicing devices.
The pressure regulating valve 1 possesses a housing 4 with a principal housing body 5, in which fluid ducts termed the primary duct 6 and the secondary duct 7 run. These two ducts respectively open at one end at the interfaces 2 and 3 with the formation of a primary connection 8 and a secondary connection 9 on the outer side of the housing. During operation of the pressure regulating valve 1 compressed air at the primary pressure may be supplied by way of the primary connection 8. Compressed air at a secondary pressure may be tapped at the secondary connection 9 and may be passed on to one or more loads, the secondary pressure as a rule being less than the primary pressure and being able to be set using the pressure regulating valve as needed. The primary and the secondary duct 6 and 7 are connected with one another by way of a transfer opening 12, which is surrounded by a primary valve seat 13. The fluid connection produced by the transfer opening 12 between the primary and the secondary ducts 6 and 7 is controlled by shifting control member 14, which has a primary control section 15 and is able to be moved in relation to the primary valve seat 13 into a closed position or into different open positions. The control member 14 accordingly possesses a continuous control characteristic, the primary control section 15 being in sealing engagement with the primary valve seat 13 in the closing position and so separates the primary duct 6 from the secondary duct 7, whereas in the open positions there is a smaller or larger distance between the primary control section 15 and the primary valve seat 13, which provides a greater or smaller transfer cross section between the primary duct 6 and the secondary duct 7 for the compressed air or some other fluid pressure medium.
The control member 14 is designed like a plunger in the working example and possesses an elongated plunger body 16, whose rear terminal part 17 runs in a recess 18 in the housing. The primary control section 15 is preferably a part of a pot-like sealing body 22, which (with the opening located at the back side of the plunger body 16) is fixed on the plunger body 16, facing the floor face, the front side of the plunger body 16 of the sealing body 22 constituting the primary control section 15. The surrounding edge, facing away from the floor, of the sealing body 22 is best provided with a sealing lip 23, which surrounds a cylindrical housing projection 24 in a sliding manner with sealing contact, such housing projection 24 containing the housing recess 18. The sealing lip 23 preferably has a check valve function so that, given a suitable pressure differential, it permits fluid flow from the secondary duct 7 to the primary duct 6 and prevents flow in the opposite direction.
The pressure regulating valve 1 renders possible a substantially constant regulation of the primary pressure to be at a desired gage pressure value below the primary pressure. The desired secondary pressure may be set by a presetting means 25 at various different values. The presetting means 25 comprises a setting member 26 arranged in a moving manner in the interior of the housing 4, and defining a fluid chamber, termed the comparison chamber 27, it forming a moving wall section of such comparison chamber 27. The remaining wall sections of the comparison chamber 27 are constituted by the housing 4 so that the volume of the comparison chamber 27 is dependent on the instantaneous position of the setting member 26.
The setting member 26 could be made like a piston to ensure a sealing action between it and the housing 4 and, using a suitable piston seal, be guided for sliding movement in the housing. In the working example a diaphragm seal 28 is however employed because of lower friction, said diaphragm being free of sliding friction. Specifically, the setting member 26 possesses a rigid principal body 32, which is connected with the housing 4 by way of a diaphragm 33 manufactured of a material with rubber-elastic properties.
The comparison chamber 27 communicates by way of at least one connecting duct 34 constantly with the secondary duct 7. It is in this manner that the comparison chamber 27 is always filled with fluid, the pressure obtaining in the comparison chamber 27 normally being equal to the secondary pressure. The connecting duct 34 can accordingly also be termed an interrogation duct, which interrogates the pressure obtaining in the secondary duct 7 and transmits it to the comparison chamber 27.
Owing to the comparison pressure in the comparison chamber 27 the setting member 26 is constantly urged in an opening direction 35 as indicated by the arrow. The resulting opening force F1 is in a closing direction 36 opposed by a closing force, termed the presetting force F2, such closing force being produced by a spring means 37 whose biasing action is able to be set.
The spring means 37, which is preferably constituted by a helical compression spring, extends in the working example in a spring chamber 38 delimited by the housing 4, such chamber being formed preferably in an elongated covering plate 42 mounted on the principal body 5 of the housing and resembling a hollow body. Via one or more outlet ducts 43 extending through the housing 4, the spring chamber 28 is constantly connected with the outside or atmosphere so that it is at atmospheric pressure.
For setting the presetting force F2 the presetting means 25 comprises a setting means 44. In the working embodiment illustrated same comprises a rotary head 41 mounted in a rotatable manner on the covering plate 42 and which is connected with a lead screw 45 in a rotation transmitting manner, said screw being in screw threaded connection with a loading disk 46 arranged in the spring chamber 38. The loading disk 46 is not able to be rotated in relation to the housing 4 but is able to be slid in the longitudinal direction of the spring chamber 38 so that its axial position may be set by turning the rotary head 44. It acts on the outer end of the spring means 37 whose inner end thrusts against the setting member 26 in the closing direction 36. It will be clear that by changing the position of the loading disk 46 the bias of the spring means 37 and accordingly the presetting force F2 may now be varied.
The presetting force F2 could additionally or alternatively to the mechanical preset means present in the working example also be caused by fluid force or by electromagnetic proportional magnets.
The setting member 26 has at least one venting duct 47 extending through it, whose outer end is in constant communication with the atmosphere, this best being ensured by its communicating with the spring chamber 38, which is connected with the above mentioned outlet ducts 43.
The opposite inner end of the venting duct 47 constitutes a venting opening 48, which like the transfer opening 12 is also under the control of the control member 14. The cooperation together of the setting member 26 and the control member 14 hence means that there is an influence on opening and closing of the venting opening 48.